Tubing strings are commonly used in oil production and generally comprise a plurality of threaded sections coupled together with an inline pump. Under certain conditions the pump can transmit large rotational forces to the tubing string which tends to release the threaded sections of the string. As this is undesirable anchors are commonly employed for preventing rotation of the tubing string in a direction corresponding to rotation of the rotor of the pump. In other situations however it may be desirable to manipulate the tubing string by preventing rotation of the tubing string In an opposite direction to the rotation of the pump. Anchoring of the tubing string may thus be desirable in both directions when it is desirable to set or unset various components coupled inline with the tubing string.
U.S. Pat. No. 5,523,991 to Jani provides a tubing tightener which is adaptable to anchor a tubing string against either clockwise or anti-clockwise rotation. The tubing tightener however requires a complex arrangement of drag slips which are operable for anchoring the tubing string in one direction only for any particular configuration of the slips. In use, the tubing tightener is thus only arranged for anchoring the tubing string in a single predetermined direction for which the tightener is configured.
U.S. Pat. No. 6,041,859 to Blades provides an anti-rotation device in which a gripping member is pivotally mounted on a housing of the device and includes a gripping surface which is arranged to engage the surrounding well casing for anchoring in one direction of rotation only. A spring is provided to bias the gripping surface into engagement with the well casing at all times.